Theoretical study of two-dimensional boron silicide from first-principles

Abstract Using first-principles calculations and evolutionary algorithm, we predict two honeycomb (P1- and C2-type) structures of BSi with two-atom thickness. Phonon spectrum calculations show that both structures are thermodynamically stable. A weak covalent bonding interaction between B atoms along [0 0 1] direction plays a very important role in structure stability of P1- and C2-type BSi. P1-type BSi is semi-metallic, while C2-type exhibits a semiconductor band structure and has a good absorption of photons in the range of 1.5–2.5 eV that is very promising for photoelectric applications. An e22 piezoelectric coefficient of 1.65 × 10−10 C m−1 is predicted for C2-type BSi, which makes it a potential candidate for piezoelectric applications at nano-scale. Moreover, three-phonon interactions are adopted to evaluate phonon lifetimes, phonon linewidths and lattice thermal conductivity. Although both P1- and C2-type BSi have a similar honeycomb structure and same elements, the maximum lattice thermal conductivity of P1-type BSi is around 6 times higher than that of C2-type BSi. Additionally, P1-type BSi exhibits remarkably higher phonon lifetimes than C2-type BSi.